Hydrogenation of invertible saccharides



J Patented Apr. 28, 1942 HYDROGENATION OF INVERTIBLE SACCHARIDES James T. Power, Wilmington, DeL, assignor to Atlas Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Original application August 17,

1938, Serial No. 225,349. Divided and this application September 19, 1941, Serial No. 411,487

6 Claims.

This invention relates to the production of polyhydric alcohols by the catalytic hydrogenation of saccharides and more particularly to the production of such alcohols by the catalytic hydrogenation of saccharides under acid conditions.

Heretofore the production of polyhydric alcohols by the catalytic hydrogenation of sugars has been carried out in non-acid, i. e. neutral or alkaline, solution, namely with a pH of 7.0 to 12.0, using specially activated metallic catalysts to shorten the reduction time and thereby prevent undue decomposition of the sugar, which readily occurs, especially when operating in alkaline solution. In general, the catalytic hydrogenation of sugars in alkaline solution is accompanied by alkaline isomerization which forms a plurality of sugars which yield a plurality of polyhydric alcohols upon reduction, and also by alkaline degradation of sugar which causes the formation of organic acids and other objectionable organic compounds which give the product undue color and odor and otherwise contaminate it.

The principal object of this invention is the reduction of saccharides to polyhydric alcohols by catalytic hydrogenation of a solution of the saccharides which is initially acid and which is maintained throughout the reduction in an acid condition. Another object of the invention is the reduction of saccharides to polyhydric alcohols by catalytic hydrogenation, while avoiding alkaline conditions in the hydrogenation reaction, thereby overcoming the deleterious effects of such alkaline conditions upon the product and the yield. Another object is the catalytic hydrogenation of saccharides without or with very little production of saccharide isomers and consequently without or with very little production of the corresponding reduction products of saccharide isomers. A more particular object is to devise a process whereby hydrolysis of polysaccharides or disaccharides and reduction of the hydrolysate may proceed simultaneously. Other objects of the invention will more fully hereinafter appear.

In the reduction of monosaccharides to polyhydric alcohols, the nature of the polyhydric alcohol product depends upon the type of monosaccharide selected. Reduction of pure aqueous solutions of glucose typically yields sorbitol almost exclusively, and no mannitol, and therefore it may be said that aldoses upon direct reduction typically yield a single polyhydric alcohol almost exclusively. Reduction of pure aqueous solutions of fructose typically yields a mixture of sorbitol and mannitol almost exclusively, and therefore it may be said that ketoses upon direct reduction typically yield a plurality of polyhydric alcohols. Under alkaline conditions, however, a different picture is presented. Thus in the reduction of glucose under alkaline conditions numerous other reactions take place, among which is the well-known Liibry de Bruyn transformation whereby the glucose is partially converted into mannose and fructose. Reduction of the unconverted glucose yields sorbitol, reduction of the mannose yields mannitol and reduction of the fructose yields sorbitol and mannitol, and so the polyhydric alcohol product will typically contain chiefly sorbitol and mannitol. Similarly in the reduction of fructose under alkaline conditions, the fructose will be partially converted to glucose and mannose, and a mixture of sorbitol and mannitol will result. Consequently it may be said that under alkaline conditions of reduction, both aldoses and ketoses typically yield a mixture of polyhydric alcohols.

This invention makes possible the substantial prevention of the transformation referred to and therefore substantially prevents the formation of the reduction products of such transformation. Consequently when glucose is reduced in accordance with the invention substantially no manni tol will be produced. However, it is to be understood that when a ketose sugar is reduced in accordance with the invention, while substantially no such transformation will occur, nevertheless a mixture of polyhydric alcohols will be produced since theoretical considerations predict the production of such a mixture by direct reduction of such a sugar.

The process of this invention in its broadest aspect involves the catalytic hydrogenation of saccharides under acid conditions until the reduction of the saccharide to the polyhydric alcohol or alcohols has been carried out to the desired extent. More specifically the invention involves the use of heat and pressure and of a hydrogenating metal catalyst such as reduced nickel. In the case of monosaccharides the process of the present invention generally produces substantial quantities of polyhydric alcohols containing the same number of carbon atoms as the starting saccharide. In the case where the disaccharide sucrose is taken as the starting sugar, it is probably not reduced directly but is probably first hydrolyzed to fi-carbon atom monosaccharides which are then reduced to the corresponding polyhydric alcohols. The disaccharide lactose, depending upon conditions, may be reduced in whole or in part to lactositol, or may be inverted in whole or in part to glucose and gelactose which are then reduced. Where invert sugar (which is a mixture of equal quantities of glucose and fructose) is taken as the starting sugar, the reduction produces a polyhydric alcohol mixture containing 25% of mannitol, the balance being a sorbitol-containing product of either low or high sorbitol content, and of excellent color. In many cases polyhydric alcohols having fewer carbon atoms than the original sugar, may be produced. In general the type of product yielded by the process described herein will be determined in large measure by the type of starting sugar selected, although the type of product obtained may be varied to a considerable extent by the conditions of the reduction, and especially by the pH of the initial mixture.

Various monoand di-saccharides, such as glucose, invert sugar (such as that prepared by the inversion of sucrose with sulfuric acid by known processes), sucrose, dextrine, black strap molasses, Hydrol which is the molasses from manufacture of glucose from corn syrups and which contains glucose, oligosaccharides (di-, tri, and tetra-saccharides) and dextrine, lactose, invert lactose, and rare sugars such as d-galac tose, 1-fucose, l-rhamnose, di-xylose, etc., or mixtures of the foregoing, may be successfully reduced to the corresponding polyhydric alcohol or alcohols by the process of the present invention. A valuable feature of the invention is that in the case of polysaccharides such as dextrine, and oligosaccharides such as sucrose, and lactose, conditions may be selected such that hydrolysis to monosaccharides and reduction of the monosaccharides produced take place substantially simultaneously. However, in the case of a reducing disaccharide such as lactose, conditions may be such that reduction to lactositol takes place either to the substantial exclusion of inversion or in addition to inversion.

In place of using pure neutral monosaccharides, the acid mixtures of hydrolyzed products obtained by hydrolyzing polysaccharides or oligosaccharides with acid may be used directly in the process. In this manner the addition of acid in the preparation of the initial mixture is dispensed with. This facilitates carrying out the process by the elimination of the steps of removal of the hydrolyzing acid, and renders the process less expensive.

The saccharide selected is mixed with a suitable medium, preferably water, to form a mixture of suitable concentration for reduction. The amount of water in the initial mixture should be sufiicient to enable the reduction to proceed, under the conditions of temperature and pressure employed, without burning, charring, or caramelization of the organic components during the reaction. In practice, it is preferred to use a 30-50% concentration, although concentrations outside of this range, such as concentrations above 50% or below 30%, may be employed if desired.

Acid is added to the aqueous saccharide mixture thus prepared, in such amount as to yield a mixture of the sugar, acid and water having a pH of below 7.0. In general in the reduction of monosaccharides capable of yielding sorbitol, the lower the pH of the initial sugar solution, that is, the greater the amount of acid present, the lower the sorbitol content of the polyhydric alcohol product.

In the case where a polysaccharide or an oligosaccharide has previously been subjected to hydrolysis with an acid, the mixture of monosaccharide and acid obtained may be diluted with water to the desired-concentration of sugar and acid, adjusted, if desired, to the desired pH by the addition of acid or of alkali, and subjected to catalytic hydrogenation under the conditions outlined below. Thus sucrose may be inverted with sulfuric acid, and the inverted mixture containing the inverting acid, diluted with water to the correct concentrations of sugar and acid, and the resulting solution subjected to reduction. Lactose may be similarly inverted to galactose and glucose prior to the reduction, if desired.

Examples of acids which may be used are: inorganic acids such as sulfuric acid, boric, and phosphoric acids, and organic acids such as acetic acid. Other acids may be used provided they are of a type which do not attack the catalyst and the reactants to an objectionable extent. In place of using a single acid, a plurality of acids may be employed, if desired.

The amount of acid present in the initial mixture is variable within the range necessary to produce an initial pH below 7.0 and as low as 1.0. Greater amounts of acid than that necessary to yield a pH lower than 1.0 are generally not desirable because of tendency to charring and discoloration upon reduction.

As the catalyst for carrying out the reduction,

any base metal or other suitable reducing catalyst may be used, but it is preferred to use a base metal reducing catalyst such as nickel. Three types of nickel catalyst which have been found very suitable for use in the practice of the invention are: reduced nickel supported on diatomaceous earth (kieselguhr) Raney nickel catalyst and reduced nickel chromate supported on diatomaceous earth. Descriptions of exemplary methods of preparation of each of these catalysts are as follows:

Sorronrrn NICKEL CATALYST Preparation of catalyst for reduction cipitate was filtered with suction and washedwith 4 portions of 125 ml. distilled water, then dried in an oven at C. for 16 hours. The cake was pulverized, then re-dried for 4 hours. The weight of the catalyst preparation was 358.8 rams. The acid washed diatomaceous earth was prepared as follows:

250 grams diatomaceous earth in the form known as Super Cel was digested on a steam bath with 1 liter of C. P. nitric acid (sp. gr. 1.42) for 21 hours in a porcelain dish. The mass was taken up in 1 liter of distilled water and filtered on a 19 cm. Buchner funnel, then washed with distilled water until the washings were just faintly acid to methyl red. The mass was dried in an oven at 110 C. and stored in stoppered bottles.

Reduction of catalyst 7.5 grams of the above catalyst preparation were placed in a glass combustion tube (Corning #172) 15 mm. x 600 mm. and held in place with a small plug of glass wool. The catalyst was I evenly distributed over seven inches of the tube allowing a free gas space past the material.

The tube was placed in an electric combustion furnace and after being swept out with a rapid stream of hydrogen was heated to 450 C. for one hour with a continual flow of hydrogen of 5060 cc./min. as measured at the exit end of the tube with a pneumatic trough. The tube was then removed from the furnace and allowed to cool while a slow stream of hydrogen was passed over the catalyst. The reduced catalyst was kept in an atmosphere of hydrogen. When charging the catalyst into the bomb, a rapid stream of hydrogen was passed through the tube. The catalyst was used within 3 hours after its preparation was complete.

RANEY NICKEL CATALYST 30 grams of Raney nickel powder (an alloy of 50% nickel and 50% aluminum) were digested with 30 grams of NaOH made up with water to 150 grams for 2 hours. The catalyst powder was added to the caustic solution in small portions over a period of 15 minutes, then heated almost to boiling for 2 hours, then evaporated until the temperature became 140 C. The mixture Was then taken up with distilled water to the original volume and boiled one-half hour. The leached catalyst was washed by decantation with 300 ml. water eight times, allowed to stand overnight under water, decanted off and was then ready for use. The catalyst obtained weighed 15 grams and was in the form of a light gray precipitate.

SUPPORTED NICKEL CHROMATIC CATALYST 150 grams of nickel nitrate hexahydrate and 12.5 grams of ammonium chromium alum dissolved in 207 ml. of distilled water were ground in a ball mill for 24 hrs. with 150 gms. of acid washed diatomaceous earth. The mixture was poured slowly with stirring into a solution of 88 gms. of ammon um carbonate in 520 m1. of distilled water. The precipitate was filtered with suction, washed with distilled water, and then dried in an oven at 120 C. for 36 hours. The dried material was reduced in a stream of hydrogen at 450 C. for 1 hour with a hydrogen flow of 60-100 cc, per minute.

Frequently the catalyst is somewhat alkaline, and its addition causes a slight rise in the pH of the mixture of water, saccharide and acid. Usually this rise will not be sufiicient to bring the pH up to, or over 7.0. If this rise is suflicient to bring the pH up to, or over, 7.0, this efiect should be compensated for by adding to the aqueous saccharide mixture a slight excess of acid, suflicient to cause the pH of the mixture containing the catalyst to be at the proper figure. This addition of acid may be either before or after the addition of the catalyst.

The amount of catalyst employed is preferably from 5 to 15% on the weight of sugar taken for reduction. The use of amounts of catalyst above 15% is permissible but does not produce sufficient shortening of the time of reduction to be warranted while the use of amounts of catalysts below 5% frequently increases the length of time of reduction to such an extent as to render the process uneconomical. Within the range set forth above, it is preferred to use of catalyst, since this amount produces substantially maximum acceleration of the reaction. Under certaln circumstances as where some other factor in the reaction is not at a desirable value, as for example, where the hydrogen pressure available is slightly lower than desired, it may be desirable to increase the amount of catalyst up to 15%, or even higher, in order to compensate for the retarding effect of lowered pressure.

Reduction may be carried out in any suitable type of apparatus wherein the reaction chamber is closed and is capable of withstanding the pressures and temperature employed. The process may be carried out either as a batch process in an autoclave, or it may be carried out continuously in apparatus designed for continuously subjecting the reaction mixture simultaneously to the action of the catalyst, to the high pressure of hydrogen required and to the proper temperature, for a suflicient length of time to complete the reduction. The apparatus should be such that the reacting mixture is subjected to agitation, in order that the reaction may proceed uniformly in all parts of the reacting mixture. In the case of continuous apparatus, the continuous movement of the liquid reacting mass is sufficient to accomplish this result. In the case of batch operation in an autoclave, externally driven stirrers or shaking devices may be used, or other methods of securing the desired agitation may be employed.

In preparing to carry out the reduction using an autoclave, the saccharide, water and acid are first charge into the autoclave in any order or manner. If desired, the previously prepared mixture of saccharide, water and acid may be charged into the autoclave or the separate ingredients may be added and the mixture stirred for complete and homogeneous intermingling. The catalyst is next added, preferably without contact with air in order to avoid oxidation of the catalyst. The autoclave is now closed and connected to a high pressure hydrogen supply. The pressure of hydrogen gas within the autoclave is allowed to build up to the desired extent, whereupon the autoclave is sealed off and disconnected from the hydrogen line and the reduction is begun by heating, accompanied by continuous agitation of the contents of the autoclave.

The reduction is carried out at a pressure considerably above atmospheric, usually around 1500 lbs. per sq. inch in order to cause the reaction to proceed at a rate which is commercially feasible. Greater initial pressure does not produce sufficiently greater speed of reaction to warrant the expense involved. However, lower initial pressures, say as low as 500 lbs. per sq. inch may be used. During the course of the reaction the pressure may rise as much as 500 lbs. per sq. inch due to the elevation of the temperature so that the maximum pressure during the reaction may be as high as 2000 lbs. per sq, inch but this may be compensated for to some extent by absorption of hydrogen as the reduction proceeds. Therefore, the range of pressure employed in the reduction is generally from 500-2000 lbs. per sq. inch.

The temperature at which the reduction is carried out is preferably in the neighborhood of from C. to 160 C. A temperature of C. is especially desirable in that the reaction proceeds at maximum speed at this temperature with very little danger of charring or discoloration. Temperatures above C. cause an undue tendency towards charring. However, temperatures below 140 0., down to room temperature (say 20 C.), may be used if desired.

The reduction is generally allowed to proceed until substantially all of the sugar has been reduced. In the case where an autoclave is used,

it will usually take from 50 to 75 minutes to bring the temperature of the reaction mass up to the preferred figure of 150 C. The time during which the preferred temperature will be maintained will vary considerably, but in general, heating is continued until the reduction has been carried to the desired degree of completion. In most instances this time will approximate 90 minutes, although it maybe greater than this for greater completeness of the reduction. In general, this time at the preferred temperature will fall within the range of one to three hours.

Upon completion of the reaction the heating and agitation of the reaction mass are discontinued, and the pressure of hydrogen is reduced to atmospheric in the case of a batch process employing an autoclave, or the reacted mass is removed from the reaction zone in the case of a continuous process. The liquid mass of reduced sugar, acid, and catalyst is removed from the vessel and filtered. The filtrate is then treated to recover the polyhydric alcohol contained therein by known processes.

By hydrogenation under acid conditions in accordance with the principles of this invention, control over the purity and type of products is extended to a point heretofore unattainable. For example, the reduction of glucose in accordance with the present invention, accomplishes the direct production of 'tol syrups which are substantially or completely mannitol-free, which have either low or high sorbitol content, as determined by pyridine number, as desired, and which are of good color, whereas reduction under alkaline conditions yields a product containing considerable quantities of mannitol, organic acids and other decomposition products. In accordance with the invention, monosaccharides and lactose can be reduced in acid solution mainly to the corresponding polyhydric alcohol or alcohols, and polysaccharides and other oligosaccharides to the polyhydric alcohols corresponding to the monosaccharides derivable therefrom by hydrolysis, since little or no isomerization to other sugars takes place and therefore little or no reduction product of such isomeric sugars is produced. This enables the ready production of sorbitol and sorbitol syrup of high purity (high pyridine number) from the corresponding saccharides. In the reduction of saccharides in acid solution, the preponderant polyhydric alcohol or alcohols in the product may be those corresponding to the saccharide employed, there being little or no polyhydric alcohol formed by reduction of saccharide isomers. On the other hand, the product may contain in addition to substantial quantities of the corresponding polyhydric alcohol or alcohols, substantial or preponderant amounts of other polyhydric bodies which are not formed by reduction of saccharide isomers, for example, polyhydric alcohols such as the desoxy polyhydric alcohols as for example desoxy hexitols and desoxy pentitols or polyhydric bodies which are not true polyhydric alcohols as for example anhydro derivatives of polyhydric alcohols. In this manner there may be produced from glucose, without the production of mannitol, products of low sorbitol content (low pyridine number) and containing, in addition to sorbitol, a relatively large amount of other polyhydric alcohols, such as desoxy polyhydric alcohols, for example desoxy hexitols such as saccharitols, desoxy pentitols, etc., and a substantial amount of still other polyhydric bodies such as anhydro hexitols. an aliphatic polyhydric alcohol in which a hy droxyl group has been replaced by hydrogen. By

"saccharitoP is meant hexitol in which one hydroxyl group is replaced by hydrogen.

This it will be seen that the reduction of glucose under acid conditions is capable of yielding directly a low pyridine number sorbitol syrup (pyridine number not over approximately 50) and no or substantially no mannitol. Such a syrup is very advantageous since it shows no crystallizing or gelling tendencies even in concentrations as high as solids due to its com plexity and is therefore very well suited for conditioning applications. This syrup is obtained immediately from glucose and in the highest possible yield since substantially no mannitol is formed. Examples of the preparation of such a syrup are Examples l3, l5 and 16 below. In general, such a product is produced by reducing in a solution of low pH.

Attempts to reduce glucose to sorbitol without simultaneous production of large amounts of mannitol under alkaline conditions above pH'l, using pressure catalytic hydrogenation are not successful because the isomerization of glucose to fructose and mannose take place and the isomeric hexahydric alcohols are produced upon reduction of these sugars. On the other hand, when reduction takes place under acidconditions, enolization of glucose is reduced to a minimumor is completely eliminated and the product consists essentially of sorbitol and nonhexitol components.

Examples of preferred methods of carrying out the invention are given below. It is to be understood that these examples are illustrative only and that the invention is not to be limited thereto, but is to be limited only asset forth in the appended claims. In the examples where reference is made to glucose, anhydrous crystalline glucose known as cerelose is intended. The pH referred to in the examples was measured with a glass electrode. In the examples, upon completion of charging with hydrogen, the pressure was as indicated, and no further hydrogen was introduced during the reduction. A heating was begun the pressure rose. As the reaction proceeded, the pressure dropped to some extent due to absorption of hydrogen, so that in some cases the hydrogen pressure at the end of the reduction may be slightly lower than at the beginning. These factors will be dependent largely upon the size of the autoclave and the volume of free space after charging. In these examples the reacting mixture was shaken continuously throughout the reduction. In these examples the weight of supported reduced nickel catalyst is in terms of its weight before the reduction described above in the preparation of the catalyst. U

EXAMPLE 1 Reduction of glucose in solution made acid with sulfuric acid-initial pH 2.9

65.2 gms. of glucose in the form of 36.4% solution in distilled Water were acidified with sulfuric acid to a pH of 1.75. The resulting solution was introduced into an autoclave, filled with carbon dioxide. 8.675 grams of supported nickel catalyst were introduced into the autoclave. The pH of the solution then became 2.9. The autoclave was closed, and hydrogen was introduced to a pressure of 1500 lbs. per square inch gauge. Heating of the autoclave was commenced. After By desoxy polyhydric alcohol is meant a 60 minutes the temperature had reached 147' C. Heating was continued for 1% hours, the temperature rising gradually to 152 C. The autoclave was cooled and its contents were removed and filtered. The pH of the reduced solution was 5.9. Analysis of the reduced solution showed that 99.41% of the sugar had disappeared. The filtrate was evaporated to a thick syrup of sorbitol which had a pyridine number of 81. The yield was 96.9%.

EXAMPLE 2 Reduction of glucose in solution made acid with acetic acid-initial pH 3.7

65.1 gms. of glucose were dissolved in water to form a 36.4% solution. 0.65 cc. of glacial acetic acid were added lowering the pH to 3.2. 8.675 gms. of supported nickel catalyst as in Example 1 were added. The pH of the mixture was now 3.7. The mixture was treated with hydrogen in an autoclave for 2 hours and 20 minutes, using an initial hydrogen pressure of 1500 lbs. per sq. inch gauge. The autoclave was heated to 150 C. which required 50 minutes and was kept at that temperature for the balance of the period. At the end of the period 99.95% of the glucose had been reduced and the pH was 5.1. The contents were filtered and the filtrate was evaporated to a thick sorbitol syrup which crystallized in a few days to a hard horny mass. The product had a pyridine number of 78.5. The yield was 94.5%.

EXAMPLE 3 Inversion of sucrose with sulfuric acid followed by reduction-initial pH 6.3

65 gms. of invert sugar made by inversion of sucrose with sulfuric acid, without neutralization or separation of the inverting acid, were dissolved in water to give a 36.4% solution. The solution thus obtained was introduced into an autoclave. It had a DH of 2.8. 8.645 grams of supported reduced nickel catalyst were added. The pH of the solution in the autoclave was now 6.3. Hydrogen was pumped in to a pressure of 1500 lbs. per sq. inch. The autoclave was heated to 150 C. in 50 minutes. The temperature was maintained at 150 C. for one and one-half hours. The autoclave was then cooled and its contents were removed. The pH was now 6.0 and 99.5 of the invert sugar had been reduced. The products consisted of approximately 25% mannitol and 75% sorbitol. After separation of the mannitol and evaporation of the sorbitol solution, a sorbitol syrup was obtained having a pyridine number of 77.

EXAMPLE 4 Reduction of glucose in solution made acid with sulfuric acid-initial pH 6.1

100 grams of glucose were dissolved in 170 ml. of distilled water containing 2 drops of concentrated sulfuric acid and made up to a total of 275 grams by adding a small amount of water. The pH of the solution was 3.2. 206.25 grams of this solution were introduced into a steel bomb of 540 cc. capacity which had been swept out with carbon dioxide. grams of freshly supported reduced nickel catalyst were introduced. The mixture was shaken to render it homogeneous. A 28 gram sample was withdrawn and its pH measured as 6.1. The weight of glucose in the bomb was now 65.2 grams. The bomb was closed and hydrogen was introduced to a pressure of 1500 lbs. per sq. in. The initial temperature was 35 C. Heating of the bomb was commenced. The temperature was raised to 150 C. in one hour and was maintained between 146 and 152 C. for one and one-half hours. The bomb was then cooled, and its contents were removed and filtered. The pH of the reduced mixture was 6.3 and tests showed that 99.5% of the glucose had been reduced. The yellow filtrate was decolorized by treatment with 1% of the activated carbon known as Darco G60 and was evaporated to 53 gms. of a thick syrup containing 87 /2% solids. The pyridine number of the product was 89.2.

EXAMPLE 5 Reduction of glucose in solution made acid with sulfuric acid.initial pH 2.1

400 gins. of glucose were dissolved in 600 grams of distilled water containing 0.4 gm. of sulfuric acid and gave a solution having a pH of 2.0. 40 grams of supported reduced nickel catalyst were added to the solution in a three-liter autoclave. The pH of the solution was now 2.1. Hydrogen was introduced to a pressure of 1500 lbs. per sq. inch and heating was commenced. In one hour the temperature was 148. It was maintained at between 148 and 152 C. for three hours. At the end of the run the pH was 5.2 and 93.1% of the glucose had been reduced. There was recovered a sorbitol syrup containing 84.9% of solids. The pyridine number of the sorbitol product was 70.

EXAMPLE 6 Reduction of glucose in acid solution using boric I acid-initial pH 5.0

400 grams of glucose were dissolved in 600 grams of distilled water containing 0.2 gram of boric acid (H3303). The resulting solution had a pH of 4.2. To this solution in a steel bomb was added 40 grams of freshly reduced supported nickel catalyst. The pH of the mixture was now 5.0. Hydrogen was introduced to an initial pressure of 1500 lbs. per sq. inch and heating was begun. After one hour the temperature had reached 147 C. It was kept between 147 and 150 C. for one hour and 50 minutes, at the end of which time 97.3% of the glucose had been reduced and the pH was 5.3. The reduced solu tion was recovered in the form of an syrup of sorbitol having a pyridine number of 92.

EXAMPLE 7 Reduction of glucose in acid solution using boric acid and Raney nickel catalystinz'tial pH 4.3

A solution of 400 gms. of glucose, 600 gms. of water and 0.5% H3303 based .on the glucose, was placed in an autoclave. The pH was now 3.6. The catalyst obtained from 30 grams of Raney nickel powder as above was added to the solution. The pH of the solution was raised to 4.3. The solution was brought to C. in one hour and maintained at 145150 C. for 2 hours, with an initial hydrogen pressure of 1500 lbs. per sq. inch. The reduced solution had a pH of 4.3. 99.5% of the glucose had been reduced. The sorbitol was recovered in the form of a 91.3% light yellow syrup having a pyridine number of EXAMPLE 8 Reduction of glucose in a solution made acid with acetic acid-initial pH 4.2

65.2 gms. of glucose in the form of 36.4% aqueous solution, containing 0.1% acetic acid, based on the weight of glucose, was introduced into a 540 cc. autoclave. ,The pH was 3.6. 8.645 grams of supported reduced nickel catalyst were added, whereupon the pH was 4.2. The autoclave was then charged with hydrogen at a pressure of 1500 lbs. per sq. inch. Heating was then commenced, 55 minutes being required to attain the operating temperature of 150-152 C. The mixture was maintained at this temperature for 90 minutes. At the end of the reduction the solution had a pH of 5.8 and was 99.6% reduced. The reduced solution was filtered, evaporated, and decolorized with 1% of activated carbon known as Darco G-60, forming a light yellow syrup of sorbitol of 91.3% concentration and having a pyridine number of 88.

EXAMPLE 9 Reduction of glucose in a solution made acid with acetic acidinitial pH 2.8

400 grams of glucose in the form of a 40% aqueous solution containing 2.5% of acetic acid on the weight of the glucose, and having a pH of 2.7 were admixed with 40 grams of freshly reduced supported nickel catalyst. The pH was now 2.8. The mixture was placed in an autoclave and hydrogen was introduced to a pressure Reduction of invert sugar in acid solution made acid by the inverting sulfuric acidinitial pH 3.2

399 gms. of invert sugar (400 gms. based on 100% inversion) made by inverting sucrose with sulfuric acid, actually only 94.6% inverted, were made up to a aqueous solution with water. The solution had a pH of 2.3. 50 grams of reduced supported nickel catalyst were added. The pH was now 3.2. The mixture was brought to 148 C. in one hour under an initial hydrogen pressure of 1500 lbs. per sq. inch, and was maintained at 148-150 C. for 90 minutes. At the end of this period the pH was 5.7 and 97.6% of the sugar taken had been reduced. Upon recovery 24.2% of mannitol and 75.8% of sorbitol was obtained. The yield of total polyhydric alcohol was 93.5% of the theoretical. The sorbitol was recovered as a water white syrup having a pyridine number of 83.5.

EXAMPLE 11 Inversion and reduction of sucrose in acid solution using sulfuric acid-initial pH 1.7

380.1 gms. of sucrose (equivalent to 400 gms. of invert) were dissolved in 619.9 gms. of water containing 0.22% of sulfuric acid based on the weight of potential invert. The solution had a pH of 1.6. 50 gms. of supported nickel catalyst were added to the solution. The pH was now 1.7. The mixture was subjected to hydrogen at an initial pressure of 1500 lbs. per sq. inch. Heating was begun, the mixture being brought to a temperature of 150 C. in 65 minutes and maintained between 149 and 152 C. for 235 minutes. The pH was now 6.0 and 98% of the sugar had been reduced. The product yielded 25.6% of mannitol and 74.4% of sorbitol. The sorbitol was in the form of a water white syrup having a pyridine number of 81.

EXAMPLE 12 Reduction of lactose in a solution containing sulfuric acid-initial pH 2.0

400 gms. of lactose hydrate (milk sugar) were dissolved in 600 gms. of distilled water containing 0.22% of sulfuric acid based, on the weight of milk sugar. The solution had a pH of 1.8 which was increased to 2.0 upon addition of 50 grams of supported reduced nickel catalyst. The solution was reduced with hydrogen at an initial pressure of 1500 lbs. per sq. inch, while being heated to 150 C. in 65 minutes and being maintained at 147-150 C. for minutes. At the end of this time solution was 98% reduced. The solution was filtered and evaporated to a thick lemon yellow syrup which did not crystallize. The product appeared to be lactositol, since it did not reduce Fehlings solution but after hydrolysis with sulfuric acid it did reduce Fehlings solution.

EXAMPLE 13 Reduction of Hydrol in acid solutioninitial pH 4.5

A 30.0% aqueous solution of Hydrol (molasses from glucose manufacture) had a pH of 4.5.

After adding supported reduced nickel catalyst EXAMPLE 14 Reduction of glucose in aqueous solution made acid with phosphoric acidinitial pH 2.0

400 gms. of glucose were dissolved in water to form'a 40% solution. 1% of phosphoric acid, based on the weight of the glucose, was added. The solution had a pH of 2.0. 40 grams of supportednickel catalyst was added. The pH re mained at 2.0. Hydrogen was introduced to an initial pressure of 1500 lbs. per sq. inch. The mixture Was then brought to 150 in 65 minutes. It was maintained at this temperature for 235 minutes. The reduction was then discontinued and the reduced mixture, which had a pH of 5.2

EXAMPLE 15 Reduction of glucose in acid solution made acid with sulfuric acid--initial pH 1.0

400 grams of glucose were dissolved in water to form a 40% solution and the solution was acidified with 1% of sulfuric acid based on the amount of sugar taken. The resulting mixture had a pH of 1.0. 40 gramsof freshly reduced supported nickel catalyst were added and the pH remained at 1.0. The mixture was then reduced with hydrogen in an autoclave using an initial pressure of 1500 lbs. per sq. inch. The temperature was raised to 150 C. in 70 minutes and was kept at 148-l50 C. for 230 minutes. The pH of the reduced solution was 4.9 and analysis showed that 95.6% of the sugar had been reduced. Recovery of the sorbitol yielded a sorbitol syrup having a pyridine number of 44. The yield was 87.8% of the theoretical.

EXAMPLE 16 Reduction of glucose in aqueous solution made acid with boric acid-initial pH 3.0

A 40% aqueous solution of glucose containing 400 grams of glucose was acidified with of boric acid based on the amount of glucose taken. This gave a solution having a pH of 3.0. To this solution was added 40 grams of supported reduced nickel catalyst. The pH of the mixture containing the catalyst was 3.0. The mixture was reduced in an autoclave using an initial hydrogen pressure of 1500 lbs. per sq. inch. The temperature was raised to 150 C. in one hour and maintained between 147 and 150 C. for two hours. The reduced product had a pH of 3.4 and was 93.5% reduced. Recovery of the product yielded sorbitol syrup having a pyridine number of 47 and a small amount of manm'tol. The yield was 97% of the theoretical. Of the total yields, 1.7% was mannitol.

EXAMPLE 17 Reduction of glucose in aqueous solution made acid with acetic acidinitial pH 3.1

A 40% aqueous solution of glucose was aciditied with 2.5% of acetic acid based on the weight of the sugar. The resulting solution had a pH of 2.7. 12.5% of freshly reduced supported nickel catalyst based on the weight of sugar taken was added to the solution, whereupon the pH became 3.1. The mixture was reduced with hydrogen in an autoclave employing an initial pressure of 1500 lbs. per sq. inch. The temperature was raised to 150 C. in an hour and maintained at 149150 C. for 90 minutes. The pH of the prodnot at the end of the run was 5.0. The solution was 99.0% reduced. Recovery of the solution gave a water white sorbitol syru having a pyridine number of 67, and a small amount of mannitol. The yield of the polyhydric alcohol was 95.6% of the theoretical. Of the total yields, 0.87% was mannitol.

EXAMPLE 18 Reduction of glucose in solution made acid with boric acid-initial pH 4.5

400 grams of glucose were dissolved in 600 grams of distilled water containing 0.2% of a gram of boric acid. The solution thus obtained had a pH of 3.5. That amount of Raney nickel catalyst obtained from 40 gram of Raney nickel powder, as described above, was added to the sugar solution in an autoclave. The pH then became 4.5. Hydrogen was pumped in to a pressure of 2000 lbs. per sq. inch. The autoclave was shaken for 96 hours at room temperature which varied from 21 to 36 C. during the run, the average temperature being 234 C. At the end of this period of time the pressure had dropped to 1800 lbs. per sq. inch and the pH of the solution was 6.2. Analysis showed that 66% of the glucose had been reduced. Recovery of the reduced solution yielded a sorbitol syrup having a pyridine number of 83.9.

EXAMPLE 19 Reduction of glucose in solution made acid with. boric acid-initial pH 5.1

400 grams of glucose were dissolved in 600 grams of water containing .08 gram of boric acid yielding a solution having a pH of 3.8. 40 grams of supported reduced nickel catalyst were added and the pH became 5.1. Hydrogen was introduced to an initial pressure of 750 lbs. per sq. inch. No further hydrogen was added. The presure in the autoclave during the reaction was governed by the temperature, the free space in the autoclave, and the amount of hydrogen used up in the reaction. The autoclave was then heated to C. in 70 minutes and maintained between 149 and 151 C. for minutes. The final pressure was 650 lbs. per sq. inch. The pH of the reduced solution was 4.8, and analysis showed that 94.9% of the sugar had been reduced. The filtered reduced solution was evaporated to a thick, pale yellow syrup of sorbitol which had a pyridine number of 82.6.

EXAMPLE 20 Reduction of glucose in solution made acid with boric acid-initial pH 5.1

A solution of 400 grams of glucose dissolved in 600 grams of distilled Water containing .08 gram of boric acid was prepared. This solution had a pH of 3.7. 40 grams of supported reduced nickel catalyst were added whereupon the pH became 5.1. Hydrogen was introduced to a pressure of 500 lbs. per sq. inch. The temperature was raised to 150 C. in 65 minutes and maintained at that point for minutes. At the end of the reduction the pressure was 425 lbs. per sq. inch and the pH of the reduced solution was 3.7. 70.2% of the sugar had been reduced. The product yielded a sorbitol syrup having a pyridine number of 42.

By pyridine number as used herein i meant an index of sorbitol content of sorbitol-containing material. This index is determined by crystallizing sorbitol from sorbitol-containing products in the form of a sorbitol-pyridine complex, filtering the crystalline complex, adding water to it to decompose the complex into pyridine and sorbitol, driving off the pyridine by vacuum distillation with water, dehydrating the sorbitol residue and weighing it as sorbitol. The propedure is specific for sorbitol sincendother polyliydric material, sueig sjsugai mannitol, etc., exhibits the same behavionwith-pyridine. The pyridine number is the weight of sorbitol crystallized from anhydrous pyridine as above multiplied .by 100, and divided by the weight of the sample (ash, moisture and sugar free). The pyridine number for pure sorbitol is about 95. The preparation of the sorbitol pyridine complex and its treatment to free sorbitol therefrom is described by strain in J. Am. Chem. Soc. vol. 56, page 1757 (1934). The pyridine number of a sorbitol-containing product is an index of its crystallizing tendency from relatively highly concentrated aqueous solutions. The higher the pyridine number the greater the crystallizing tendency.

This application is a division of my copending appllizzation, Serial Number 225,349, filed August wryanna. I

Having described my invention, what 1 claim 1s:

1. The process of producing polyhydroxy compounds from an invertible saccharide selected from the group consisting of oligosaccharides and polysaccharides, which comprises dissolving said saccharide and acid in water to form an aqueous solution with an acid strength sufiicient to hydrolyze the saccharide, hydrolyzing the said saccharide in said acid solution to monosaccharide, and concurrently in the same operation hydrogenating said monosaccharide to polyhydroxy compounds of the same number of carbon atoms with hydrogen under pressure, in the presence of a hydrogenating catalyst, and at a temperature below that at which splitting of the carbon-carbon bond occurs.

2. The process of producing polyhydroxy compounds from an invertible saccharide selected from the group consisting of oligosaccharides and polysaccharides, which comprises dissolving said saccharide and acid in water to form an aqueous solution with an acid strength suflicient to hydrolyze the saccharide, hydrolyzing the said saccharide in said acid solution to monosaccharide, and concurrently in the same operation hydrogenating said monosaccharide to polyhydroxy compounds of the same number of carbon atoms with hydrogen under a pressure of 500 to 2000 pounds per square inch, in the presence of a hydrogenating catalyst, and at a temperature not exceeding about 160 C.

3. The process of producing polyhydroxy compounds from an invertible saccharide selected from the group consisting of oligosaccharides and polysaccharides, which comprises dissolving said saccharide and acid in water to form an aqueous solution with an acid strength suflicient to hydrolyze the saccharide, hydrolyzing the said saccharide in said acid solution to monosaccharide, and concurrently in the same operation hydrogenating said monosaccharide to polyhydroxy compounds of the same number of carbon atoms with hydrogen under a pressure of 500 to 2000 pounds per square inch, in the presence of a reduced nickel catalyst, and at a temperature not exceeding about C.

4. The process of producing six carbon atom polyhydroxy compounds from sucrose which comprises dissolving said sucrose and acid in water to form an aqueous solution with an acid strength suflicient to hydrolyze the sucrose, hydrolyzing the said sucrose in said acid solution to monosaccharides, and concurrently in the same operation hydrogenating said monosaccharides to six carbon atom polyhydroxy compounds with hydrogen under pressure, in the presence of a hydrogenating catalyst, and at a temperature below that at which the splitting of the carbon-carbon bond occurs.

5. The process of producing six carbon atom polyhydroxy compounds from sucrose which comprises dissolving said sucrose and acid in water to form an aqueous solution with an acid strength sufficient to hydrolyze the sucrose, hy-

drolyzing the said sucrose in said acid solution to monosaccharides, and concurrently in the same operation hydrogenating said monosaccharides to six carbon atom polyhydroxy compounds with hydrogen under a pressure of 500 to 2000 pounds per square inch, in the presence of a hydrogenating catalyst, and at a temperature not exceeding about 160 C.

6. The process of producing six carbon atom polyhydroxy compounds from sucrose which comprises dissolving said sucrose and acid in water to form an aqueous solution with an acid strength suflicient to hydrolyze the sucrose, hydrolyzing the said sucrose in said acid solution to monosaccharides, and concurrently in the same operation hydrogenating said monosaccharides to six carbon atom polyhydroxy compounds with hydrogen under a pressure of 500 to 2000 pounds per square inch, in the presence of a reduced nickel catalyst, and at a temperature not exceeding about 160 C.

JAMES T. POWER. 

